1. Field of the Invention
This invention relates to novel sunscreen compositions which, when applied to the human skin provides protection against the harmful effects caused by ultraviolet radiation. More particularly, this invention relates to sunscreen compositions in the form of viscous liquids and gels wherein an ultraviolet light-absorbing ingredient is placed on the skin and is provided with increased water resistant characterisics with the aid of polymeric binder. Most particularly, this invention relates to sunscreen compositions that are water proof and fulfill the guidelines established by the Food and Drug Administration, as listed in the Federal Register: Volume 43, Number 166.
2. Discussion of the Relevant Art
Sunscreen compositions are commonly used during outdoor activity. Many people have occupations which require them to be exposed to the sun for long periods of time. Others choose to use their free time in outdoor recreations e.g. sunbathing, playing golf, surfing, fishing, skiing and swimming. All of these activities promote perspiration or allow the body to come in contact with water. Numerous sunscreen compositions have been developed which absorb ultraviolet light in a region of 280 to 320 nanometers (2800-3200 Angstroms; referred to as the "erythemal region") to protect the human body against this radiation that produces erythema and skin cancer, whether the source be from the sun or from man made devices. These compositions also incorporate ultraviolet absorbing agents that absorb in the region between 320 and 380 nanometers (3200-3800 Angstroms) and should be resistant to removal from the skin by perspiration or water in order to broaden and prolong their effectiveness.
Numerous substantive sunscreen agents, and substantive and water-resistant sunscreen compositions are available today. Development of substantive sunscreen agents and sunscreen compositions containing these substantive agents are illustrated in U.S. Pat. No. 3,864,473 issued to Cicendelli; U.S. Pat. No. 4,004,074 issued to Gerecht; and U.S. Pat. No. 4,256,664 issued to Epstein. These compositions make use of sunscreen agents that are not approved by the FDA and their topical use is limited.
No known sunscreen agent, that achieves a degree of water-resistancy, has been approved by the Food and Drug Administration. FDA approved sunscreen agents have, however, been incorporated into compositions which upon application to the skin physically keep the sunscreen agent on the skin during perspiration or immersion in water. The majority of these compositions make use of polymeric materials that are either emulsified in the composition or carried to the skin by a vehicle in which a continuous polymeric film is cast on the skin.
The use of an acid form of a cross-linked co-polymer of ethylene-maleic anhydride composition in the form of a gel is illustrated in U.S. Pat. No. 3,821,363 issued to Black. The use of acrylate/acrylic acid co-polymer compositions in the form of oils and emulsions are illustrated in U.S. Pat. No. 4,172,122 issued to Kubik. In U.S. Pat. No. 4,254,102 issued to Kaplan there is described the use of compositions containing hydroxyethylcellulose in conjunction with a surface active agent and a fatty alcohol. In U.S. Pat. No. 4,193,989 issued to Eng, there is described gel compositions of hydroxypropyl cellulose acetate as the film former.
Known compositions that make use of polymers to form a continuous polymeric film in which the active sunscreen agent is homogeneously dispersed throughout the matrix of the film have numerous disadvantages. Aqueous based compositions in which the polymer is usually emulsified have long drying rates on the skin, foam on the skin during application and during the drying cycle leave the skin feeling tacky. These compositions, if not fully dried, also have a tendency to allow particulate matter, such as beach sand, to adhere to the skin. Furthermore, the water-resistant properties of these aqueous based compositions are decreased if they are not fully dried before perspiration or entry into water. The formation of a continuous protective film on the skin is prevented by compositions which make use of solvent systems because they cannot tolerate large amounts of oil and other emollients. Without the use of emollients in compositions containing alcohols, the skin may become dry and irritated. Generally these compositions are also formulated in thin solutions with low viscosities which make them difficult to apply to the skin in an even manner.
Compositions, which make use of a polyamide resin as the film former, in combination with ethanol as a solvent and are effective in resisting water wash off, are illustrated in U.S. Pat. No. 3,895,104 issued to Karg. These compositions, however, are low in viscosity, and are difficult to apply to the skin evenly thus permitting spot burning to occur, which may result in extreme pain and blistering of the skin. This effect is more pronounced with individuals having fair complexions and who normally use sunscreen products having high SPF (Sun Protection Factor) values. Water-resistant compositions described heretofore or that are currently being marketed in addition to being difficult to apply to the skin evenly, lack the ability to be made in a range of viscosities, thus limiting the formulator in his selection of ingredients to be used in a composition and separate systems must be developed to fulfill the needs of the consumer. Furthermore, compositions having high solvent concentrations lack the ability to homogeneously suspend particulate matter throughout the matrix of the composition thereby preventing the use of insoluble solid ingredients which have a tendency to prevent ultraviolet radiation from being absorbed by the skin.
The present invention overcomes the shortcomings of known water-resistant sunscreen compositions by incorporating ingredients which resist removal of the active sunscreen agent and particulate suspended matter that reflect and/or absorb ultraviolet radiation by perspiration and water when applied to the skin. The present invention, in combination with ingredients that, allow the composition to be pseudo-plastic with a range of viscosities, have the ability to suspend insoluble particulate matter, allows the composition to be applied to the skin evenly and easily to all parts of the body and protects the skin from the harmful effects of the sun's radiation. There is a need for such a product for both health and cosmetic reasons. Ingredients may be available which exhibit one or more of these desired attributes. However, the combination of these attributes for use in preparing water-proof sunscreen systems has not been demonstrated. Ingredients that have not been used previous to this invention in water-proof sunscreen compositions for fulfilling these requirements are the combination of active sunscreen agents, polyamide polymers, monohydric alcohols, acrylic acid crosslinked polymers, and alkaline neutralizing agents.